
132 Nuclear Forensic Analysis
The production of
233
U for weapons applications has many parallels with the pro-
duction
of Pu. Irradiations tend to be of short duration at high ux to minimize
the buildup of undesirable U isotopes (including
232
U). A cooling period is required
before
233
U can be recovered from the source material: it is necessary to permit
27-day
233
Pa decay to
233
U before chemical processing. And criticality safety limits
the batch size of the nal product in any reprocessing operation.
It
has been demonstrated that Th-based fuels can be used in LWRs, giving a
signicantly better conversion ratio